Capturing the Polarization Effect in Amino Acid Ionic Liquids

Area of Science:

• Computational Chemistry
• Materials Science
• Green Chemistry

Background:

• Amino acid ionic liquids (AAILs) show promise for green chemistry due to their biocompatibility and biodegradability.
• Accurate modeling of AAILs requires capturing polarization and hydrogen bonding effects, which are crucial for their structure and dynamics.
• Existing nonpolarizable force fields (FFs) struggle to represent these essential interactions.

Purpose of the Study:

• To develop and validate polarizable force fields using Drude oscillators for simulating AAILs.
• To investigate the impact of polarization effects on the structural and dynamical properties of AAILs.
• To provide a reliable computational framework for the design and application of AAILs in green chemistry.

Main Methods:

• Development of polarizable force fields (FFs) with Drude oscillators for specific AAILs ([Cho][Ala], [Cho][Gly], [Cho][Pro], [Cho][Ser]).
• Utilized quantum chemistry, symmetry-adapted perturbation theory (SAPT), and ab initio molecular dynamics (AIMD) for FF parameterization.
• Performed extensive molecular dynamics (MD) simulations to analyze structural and dynamical properties.

Main Results:

• Polarizable FFs significantly alter AAIL structural and dynamical properties compared to nonpolarizable FFs (FixQ, ScaleQ).
• Revealed slow and heterogeneous dynamics in AAILs over tens of nanoseconds, distinct from traditional ionic liquids.
• The ScaleQ model inadequately captures polarization and underestimates hydrogen bonding interactions.

Conclusions:

• Polarizable force fields with Drude oscillators are essential for accurately simulating AAILs.
• The study provides a robust foundation for understanding and designing AAILs for green chemistry applications.
• Accurate simulation of polarization and hydrogen bonding is critical for predicting AAIL behavior.